Released last month, the 2005 Federal Radionavigation Plan (FRP)–a joint production of the DOT, DOD and the Department of Homeland Security–provides a useful guide to what air navigation will be like between now and 2020. Of course, federal crystal balls occasionally can be cloudy, especially when they peer 14 years into the future. Nevertheless, since its first publication in 1980, the biennial FRP has given aviators a reasonable picture of what the future will bring, provided they accept that nothing that far ahead is cast in concrete.

The basic tenet of the plan is that in the near future the airspace environment will be satellite-dominated because GPS works well and a satellite system would allow the federal government–primarily the FAA–to gradually divest itself of the heavy financial burden of the thousands of terrestrial navaids it operates today.

Currently, there are around 1,300 NDBs, 1,050 VORs, 1,025 DMEs and 1,275 ILSes as well as marker beacons spread across the National Airspace System (NAS), along with an unspecified number of radars, airport ASDEs and ADS-B stations that don’t properly qualify as navaids.

Gradual System Phaseouts
Other government departments also operate navaids in the NAS. The DOD has several dozen of its own VOR/DMEs, Vortacs and Tacans–the latter two of which include civil DMEs–while the U.S. Coast Guard runs the nation’s 29 loran stations.

Insiders expect NDBs will be the first navaids to see cutbacks. Already, of course, the FAA has withdrawn a large number of NDB procedures, and the agency
will progressively decommission transmitter stations until all that remain are an unspecified number serving Alaska, offshore areas such as the Gulf of Mexico and what the FRP describes as “international gateways.”

VORs will follow, with a gradual reduction of facilities as GPS/WAAS and, particularly, LPV procedures become firmly established. But a minimum operating network of VORs–probably 300 to 400–will remain through 2020, primarily as backups in case of GPS failures or interference. (Interference doesn’t necessarily mean accidental events or intentional jamming by the nation’s enemies; under the FRP, the DOD is allowed to conduct GPS jamming tests in the NAS to counter those enemies.)

On the other hand, DMEs will gradually increase as low-power units will be added at several ILS locations, and others will supplement coverage in certain terminal areas and en route altitudes–suggested elsewhere as being “above FL180”–to provide continuous GPS Rnav backup service.

The phaseout of Category I and localizer-only ILS is scheduled in the federal radionavigation plan to begin around 2015, coincident with the expected introduction of the WAAS-based Category I GNSS landing system (GLS), along with improvements in the GPS satellite constellation.

One ILS will remain at every current ILS-equipped airport for backup purposes. All Category II and III installations are expected to remain operational until at least 2020, which may subtly underline the agency’s current uncertainty about the likely
introduction date of their satellite-based replacements.

Many insiders feel that loran, meanwhile, could remain an ideal GPS backup.